1. Field of the Invention
This invention relates to a method of generating poses and motions of a tree structure link system that is made by modeling of a man, animals, robots, etc., and consists of multiple links connected at joints.
2. Relating Art Statement
A conventional technologies of generating data representing the motions of man, animals, etc. which appear in animations of CG, movie works, games, etc., and, data representing the motions of robots with many joints, such as humanoids, are published in documents;    [1] Choi, K. J and Ko, H. S.: “Online Motion Retargetting,” the Journal of Visualization and Computer Animation, vol. 11, pp. 223–235, 2000,    [2] Gleicher, M. and Litwinowicz, P.: “Constraint-based Motion Adaptation,” the Journal of Visualization and Computer Animation, vol. 9, pp. 65–94, 1998, and    [3] Lee, J. and Shin, S. Y.: “A Hierarchical Approach to Interactive Motion Editing for Human-like Figures, “Proceedings of SIGGRAPH '99, pp. 39–48, 1999, etc. All of these are technology of calculating the motion that satisfies constraint conditions that a leg is not slippery to the ground, etc. by optimization calculation in order to apply motion capture data obtained previously to various man type tree structure link systems that link length etc. differs mutually, or, to make a new motion, while the feature of the motion is saved.
In the technology described in the above-mentioned document [1], the motion is calculated so that each joint angle becomes a target value given, respectively, as much as possible closely while positions of end links are fixed. In the technology described in the above-mentioned document [2], the motion meeting the constraint conditions is calculated by performing large region-optimization so that the constraint conditions may become smooth over the whole motion. In the technology described in the above-mentioned document [3], by expressing the constraint conditions with hierarchical spline functions, it makes it possible to change some poses of a part of the body, while the constraint conditions are satisfied. The optimization calculation is performed for the whole motion like the technology of the reference [2].
For the technologies of the references [1], [2] and [3], a reference motion such as motion capture data is needed. Although the cost of the motion capture compared with the former is reduced and a library of the capture data is marketed increasingly, there are drawbacks that whenever the motion that is not included in the library is needed, the new motion has to be captured, the motions made from the same library tend to be similar, and, great time and great efforts are needed for correcting the motion as a wish.
For the technologies of the references [2] and [3], there is a drawback that since the large region optimization calculation is performed, it could not be applied to real time or interactive motion generation into which the input goes sequentially.
For the technology of the reference [1], there is a drawback that if the constraint condition is added to the link other than the end link, the calculation result may diverge. Moreover, there is another drawback that if it is going to fix many links, the solution may not be obtained.
The commercial CG software comprising an interface for specifying the positions of the end links of the link structure object in order to produce the animation has a drawback that the natural pose creation is difficult, since it can only calculate the joint angle of the partial link sequence equivalent to one branch of the tree structure link system such as an arm, a leg, etc., and cannot change the pose of the whole tree structure link system.
It can specify only the end link of the link sequence as the fixed link. This is for numerical computation to fail because inconsistency arises between each constraint when there is only a small number of joint between the multiple fixed links.
The movable range of the spherical joint is not taken into consideration with the conventional technologies.